Work machine, system and method for controlling work machine

ABSTRACT

A first work machine includes a work implement. A method of controlling the first work machine includes acquiring a traveling state of the first work machine that is performing work with the work implement while traveling on a first work path, determining whether the first work machine is deviating from the first work path based on the traveling state, and stopping travel of the first work machine upon determining that the first work machine is deviating from the first work path.

TECHNICAL FIELD

The present invention relates to a work machine, a method and a systemfor controlling a work machine.

BACKGROUND ART

Conventionally, a technique for automatically controlling travel of awork machine such as a bulldozer is known. For example, in order torealize the travel along a desired straight line path, Patent Document 1discloses a technique for controlling a work implement to return to astraight line path when it has deviated from the straight line path.

CITATION LIST Patent Document

Patent Document 1: Japanese Unexamined Patent Publication 2012-36726

SUMMARY OF THE INVENTION Technical Problem

In digging work in which a work vehicle repeatedly travels back andforth on a work path called a slot to remove a surface soil, a pluralityof work vehicles perform digging work on different slots individually.Therefore, it is preferable to prevent a work machine from deviatingfrom the work path. An object of the present disclosure is to prevent awork machine traveling under automatic control from deviating from awork path.

Solution to Problem

A method according to a first aspect of the present disclosure is amethod for controlling a first work machine including a work implement.The method according to the present aspect includes the followingprocesses. A first process is to acquire a traveling state of the firstwork machine that is performing work with the work implement whiletraveling on a first work path. A second process is to determine whetherthe first work machine is deviating from the first work path based onthe traveling state. A third process is to stop travel of the first workmachine upon determining that the first work machine is deviating fromthe first work path.

A system according to a second aspect of the present disclosure is asystem for controlling a first work machine including a work implement.The system according to the present aspect includes a communicationdevice that communicates with the first work machine, and a remotecontroller. The remote controller acquires a traveling state of thefirst work machine that is performing work with the work implement whiletraveling on a first work path. The remote controller determines whetherthe first work machine is deviating from the first work path based onthe traveling state. The remote controller stops travel of the firstwork machine upon determining that the first work machine is deviatingfrom the first work path.

A work machine according to a third aspect of the present disclosureincludes a work implement, a travel device, and a machine controllerthat controls the work implement and the travel device. The machinecontroller acquires a traveling state of the work machine when the workmachine is performing work with the work implement while traveling on awork path. The machine controller determines whether the work machine isdeviating from the work path based on the traveling state. The machinecontroller stops travel of the work machine upon determining that thework machine is deviating from the work path.

Advantageous Effects of Invention

According to the present disclosure, it is determined whether the workmachine is deviating from the work path based on the traveling state.When it is determined that the work machine is deviating from the workpath, the travel of the work machine is stopped. As a result, it ispossible to prevent the work machine from deviating from the work path.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram illustrating a control system of a workmachine according to an embodiment.

FIG. 2 is a side view of the work machine.

FIG. 3 is a schematic diagram illustrating a configuration of the workmachine.

FIG. 4 is a flowchart illustrating processes of automatic operation.

FIG. 5 is a side view illustrating an example of an actual topography.

FIG. 6 is a top view of a work site illustrating an example of a workarea.

FIG. 7 is a flowchart illustrating processes of deviation preventioncontrol.

FIG. 8 is a view illustrating an example of deviation width.

DESCRIPTION OF EMBODIMENTS

A control system of a work machine according to an embodiment will bedescribed below with reference to the drawings. FIG. 1 is a schematicdiagram illustrating a control system 100 of a work machine according toan embodiment. As illustrated in FIG. 1 , the control system 100includes a plurality of work machines 1 a and 1 b, a remote controller2, an input device 3, a display 4, an operating device 5, and anexternal communication device 6. The control system 100 controls thework machines 1 a and 1 b disposed at a work site such as a mine. Theplurality of work machines 1 a and 1 b include a first work machine 1 aand a second work machine 1 b. The work machines 1 a and 1 b accordingto the present embodiment are bulldozers.

The remote controller 2, the input device 3, the display 4, theoperating device 5, and the external communication device 6 are disposedoutside of the work machines 1 a and 1 b. The remote controller 2, theinput device 3, the display 4, the operating device 5, and the externalcommunication device 6 may be disposed, for example, in a managementcenter outside of the work machines 1 a and 1 b. The remote controller 2remotely controls the work machines 1 a and 1 b. The number of the workmachines remotely controlled by the remote controller 2 is not limitedto two and may be greater than two.

FIG. 2 is a side view of the first work machine 1 a. FIG. 3 is a blockdiagram illustrating a configuration of the first work machine 1 a.Although the first work machine 1 a will be described below, theconfiguration of the second work machine 1 b is the same as that of thefirst work machine 1 a. As illustrated in FIG. 2 , the first workmachine 1 a includes a vehicle body 11, a travel device 12, and a workimplement 13. The vehicle body 11 includes an engine compartment 15. Thetravel device 12 is attached to the vehicle body 11. The travel device12 includes a pair of left and right crawler belts 16L and 16R. Thefirst work machine 1 a travels due to the rotation of the left and rightcrawler belts 16L and 16R.

The work implement 13 is attached to the vehicle body 11. The workimplement 13 includes a lift frame 17, a blade 18, and a lift cylinder19. The lift frame 17 is attached to the vehicle body 11 so as to bemovable up and down. The lift frame 17 supports the blade 18. The blade18 moves up and down accompanying the movements of the lift frame 17.The lift frame 17 may be attached to the travel device 12. The liftcylinder 19 is coupled to the vehicle body 11 and the lift frame 17. Dueto the extension and contraction of the lift cylinder 19, the lift frame17 moves up and down.

As illustrated in FIG. 3 , the first work machine 1 a includes an engine22, a hydraulic pump 23, and a power transmission device 24, and acontrol valve 27. The hydraulic pump 23 is driven by the engine 22 todischarge hydraulic fluid. The hydraulic fluid discharged from thehydraulic pump 23 is supplied to the lift cylinder 19. Although onehydraulic pump 23 is illustrated in FIG. 3 , a plurality of hydraulicpumps may be provided.

The power transmission device 24 transmits driving force of the engine22 to the travel device 12. The power transmission device 24 may be, forexample, a hydro static transmission (HST). Alternatively, the powertransmission device 24 may be, for example, a transmission having atorque converter or a plurality of transmission gears. Alternatively,the power transmission device 24 may be another type of transmission.

The control valve 27 is disposed between a hydraulic actuator such asthe lift cylinder 19 and the hydraulic pump 23. The control valve 27controls the flow rate of hydraulic fluid supplied from the hydraulicpump 23 to the lift cylinder 19. The control valve 27 may be a pressureproportional control valve. Alternatively, the control valve 27 may bean electromagnetic proportional control valve.

The first work machine 1 a includes a machine controller 26 a and amachine communication device 28. The machine controller 26 a controlsthe travel device 12 or the power transmission device 24, therebycausing the first work machine 1 a to travel. The machine controller 26a controls the control valve 27, thereby causing the blade 18 to move upand down.

The machine controller 26 a is programmed to control the first workmachine 1 a based on acquired data. The machine controller 26 a includesa processor 31 a and a storage device 32 a. The processor 31 a is, forexample, a central processing unit (CPU). Alternatively, the processor31 a may be a processor that is different from a CPU. The processor 31 aexecutes processes for controlling the first work machine 1 a accordingto programs.

The storage device 32 a includes a non-volatile memory such as a ROM anda volatile memory such as a RAM. The storage device 32 a may include anauxiliary storage device such as a hard disk or a solid state drive(SSD). The storage device 32 a is an example of a non-transitorycomputer-readable recording medium. The storage device 32 a storescomputer commands and data for controlling the first work machine 1 a.

The machine communication device 28 wirelessly communicates with theexternal communication device 6. For example, the machine communicationdevice 28 communicates with the external communication device 6 via awireless LAN such as Wi-Fi (registered trademark), a mobilecommunication such as 3G, 4G, or 5G, or another type of wirelesscommunication system.

The first work machine 1 a includes a position sensor 33. The positionsensor 33 may include, for example, a global navigation satellite system(GNSS) receiver such as a global positioning system (GPS).Alternatively, the position sensor 33 may include a receiver of anotherpositioning system. The position sensor 33 may include a ranging sensorsuch as Lidar, or an image sensor such as a stereo camera. The positionsensor 33 outputs position data to the machine controller 26 a. Theposition data indicates a position of the first work machine 1 a.

The first work machine 1 a includes an orientation sensor 34. Theorientation sensor 34 detects a traveling direction of the first workmachine 1 a. The orientation sensor 34 may include, for example, aninertial measurement unit (IMU). Alternatively, the orientation sensor34 may include a geomagnetic sensor. Alternatively, the travelingdirection of the first work machine 1 a may be detected from the changein position of the first work machine 1 a detected by the positionsensor 33. The orientation sensor 34 outputs orientation data indicativeof the traveling direction of the first work machine 1 a.

The first work machine 1 a includes a left rotation sensor 35L and aright rotation sensor 35R. The left rotation sensor 35L detects therotation speed of the left crawler belt 16L. The right rotation sensor35R detects the rotation speed of the right crawler belt 16R. The leftrotation sensor 35L outputs rotation speed data indicative of therotation speed of the left crawler belt 16L. The right rotation sensor35R outputs rotation speed data indicative of the rotation speed of theright crawler belt 16R.

The external communication device 6 illustrated in FIG. 1 wirelesslycommunicates with the machine communication device 28. The externalcommunication device 6 transmits a command signal from the remotecontroller 2 to the machine communication device 28. The machinecontroller 26 a receives the command signal via the machinecommunication device 28. The external communication device 6 receivesthe position data, the orientation data, and the rotation speed data ofthe first work machine 1 a via the machine communication device 28.

The input device 3 is a device that is operable by an operator. Theinput device 3 receives an input command from the operator and outputsan operation signal corresponding to the input command to the remotecontroller 2. The input device 3 outputs the operation signal accordingto an operation by the operator. The input device 3 outputs theoperation signal to the remote controller 2. The input device 3 mayinclude a pointing device such as a mouse or a trackball. The inputdevice 3 may include a keyboard.

The display 4 includes a monitor such as a CRT, an LCD, or an OELD. Thedisplay 4 receives an image signal from the remote controller 2. Thedisplay 4 displays an image corresponding to the image signal. Thedisplay 4 may be integrated with the input device 3. For example, theinput device 3 and the display 4 may include, for example, a touchscreen.

The operating device 5 is operable by an operator. The operating device5 includes, for example, a pedal, a lever, or a switch. The operatingdevice 5 is able to remotely control the plurality of work machines 1 aand 1 b individually. The operating device 5 may specify a portion ofthe plurality of work machines 1 a and 1 b to remotely control theportion. The work machines 1 a and 1 b can be switched between anautomatic operation mode and a manual operation mode.

In the automatic operation mode, the work machines 1 a and 1 b operateautomatically without operations by an operator. In the automaticoperation mode, the work machines 1 a and 1 b operate according to acommand from the remote controller 2 as described later. Alternatively,in the automatic operation mode, the work machines 1 a and 1 b operateautonomously and automatically. In that case, the work machines 1 a and1 b operate according to determination of the machine controller of eachof the work machines 1 a and 1 b.

In the manual operation mode, the work machines 1 a and 1 b operateaccording to an operation signal from the operating device 5. Theoperating device 5 receives an operation by an operator and outputs anoperation signal corresponding to the operation. The operation signal istransmitted to the plurality of work machines 1 a and 1 b via theexternal communication device 6.

The remote controller 2 remotely controls the work machines 1 a and 1 b.The remote controller 2 receives an operation signal from the inputdevice 3. The remote controller 2 outputs an image signal to the display4. The remote controller 2 includes a processor 2 a and a storage device2 b. The processor 2 a is, for example, a central processing unit (CPU).Alternatively, the processor 2 a may be a processor that is differentfrom a CPU. The processor 2 a executes processes for controlling thework machines 1 a and 1 b according to programs. In the followingdescription, the description regarding the processes executed by theremote controller 2 may be interpreted as the processes executed by theprocessor 2 a.

The storage device 2 b includes a non-volatile memory such as a ROM anda volatile memory such as a RAM. The storage device 2 b may include anauxiliary storage device such as a hard disk or a solid state drive(SSD). The storage device 2 b is an example of a non-transitorycomputer-readable recording medium. The storage device 2 b storescomputer commands and data for controlling the work machines 1 a and 1b.

Next, automatic operation of the work machines 1 a and 1 b executed bythe control system 100 will be described. FIG. 4 is a flowchartillustrating processes executed by the remote controller 2.

As illustrated in FIG. 4 , in step S101, the remote controller 2acquires actual topography data. The actual topography data indicates anactual topography of a work site. FIG. 5 is a side view illustrating anexample of an actual topography 80. The actual topography data includescoordinates and heights of a plurality of points on the actualtopography 80. The work machines 1 a and 1 b perform digging of theactual topography 80 by slot dozing under automatic operation so thatthe actual topography 80 has a shape along a final target topography 81.

In step S102, the remote controller 2 acquires position data. Theposition data includes first position data of the first work machine 1 aand second position data of the second work machine 1 b. The firstposition data indicates a position of the first work machine 1 a. Thesecond position data indicates a position of the second work machine 1b.

In step S103, the remote controller 2 determines a plurality of workareas 50A and 50B at the work site. FIG. 6 is a top view of the worksite illustrating an example of the work areas 50A and 50B according toa first embodiment. The plurality of work areas 50A and 50B include afirst work area 50A and a second work area 50B. The first work area 50Aincludes a plurality of first work paths 51 to 53. The plurality offirst work paths 51 to 53 extend in a predetermined first work directionD1. The plurality of first work paths 51 to 53 extend linearly. Thefirst work paths 51 to 53 are aligned in the lateral direction of thefirst work area 50A. The lateral direction of the first work area 50A isthe direction intersecting the first work direction D1.

The second work area 50B is adjacent to the first work area 50A. Thesecond work area 50B includes a plurality of second work paths 54 to 56.The plurality of second work paths 54 to 56 extend in a predeterminedsecond work direction D2. The plurality of second work paths 54 to 56extend linearly. The second work paths 54 to 56 are aligned in thelateral direction of the second work area 50B. The lateral direction ofthe second work area 50B is the direction intersecting the second workdirection D2. In the example illustrated in FIG. 6 , the first workdirection D1 and the second work direction D2 are the same. However, thefirst work direction D1 and the second work direction D2 may bedifferent directions from each other.

The remote controller 2 may determine the work areas 50A and 50Baccording to an operation of the input device 3 by an operator.Alternatively, the remote controller 2 may automatically determine thework areas 50A and 50B.

The alignment of the work paths 51 to 56 is not limited to thatillustrated in FIG. 6 and may be changed. For example, the number of thework paths in each work area is not limited to three and may be lessthan three or greater than three. The number of the work paths in thefirst work area 50A and the number of the work paths in the second workarea 50B are not limited to the same and may be different. The number ofthe work areas is not limited to two and may be greater than two.

In step S104, the remote controller 2 allocates the work areas 50A and50B to the work machines 1 a and 1 b. The operator allocates the workarea 50A to one of the wok machines 1 a and 1 b and allocates the workarea 50B to the other one using the input device 3. The remotecontroller 2 determines the work machines to be allocated to therespective work areas 50A and 50B based on the operation signal from theinput device 3.

Alternatively, the remote controller 2 may automatically determine thework machines to be allocated to the respective plurality of work areas50A and 50B. In the example illustrated in FIG. 6 , the remotecontroller 2 allocates the first work area 50A to the first work machine1 a and allocates the second work area 50B to the second work machine 1b.

In step S105, the remote controller 2 determines whether an approval tostart work has been received. The operator can instruct an approval tostart work by the work machines 1 a and 1 b using the input device 3.The remote controller 2 determines whether the approval has beenreceived based on the operation signal from the input device 3. Theremote controller 2 may determine whether the approval has been receivedfor each of the work machines 1 a and 1 b individually.

In step S106, the remote controller 2 transmits a work start command tothe work machines 1 a and 1 b. Accordingly, the first work machine 1 ais controlled to perform work according to the alignment of theallocated first work paths 51 to 53. The remote controller 2 transmitsdata indicative of positions of the first work paths 51 to 53 to thefirst work machine 1 a. The remote controller 2 transmits dataindicative of positions of the second work paths 54 to 56 to the secondwork machine 1 b.

The first work machine 1 a moves to the first work paths 51 to 53allocated to the first work machine 1 a and automatically aligns itsposition and orientation with respect to the first work paths 51 to 53.Then, the first work machine 1 a performs digging while moving along thefirst work paths 51 to 53. As a result, slots are formed along therespective first work paths 51 to 53. When the digging of the first workpaths 51 to 53 is completed, digging walls are left between the firstwork paths 51 to 53. The first work machine 1 a performs digging of thedigging walls while moving along allocated first digging wall areas 61and 62. The order of digging of the first work paths 51 to 53 or theorder of digging of the first digging wall areas 61 and 62 may bedetermined by the remote controller 2. Alternatively, the order ofdigging of the first work paths 51 to 53 or the order of digging of thefirst digging wall areas 61 and 62 may be determined by the machinecontroller 26 a of the first work machine 1 a.

Similarly, the second work machine 1 b moves to the second work paths 54to 56 allocated to the second work machine 1 b and automatically alignsits position and orientation with respect to the second work paths 54 to56. Then, the second work machine 1 b performs digging while movingalong the second work paths 54 to 56. When the digging of the secondwork paths 54 to 56 is completed, digging walls are left between thesecond work paths 54 to 56. The second work machine 1 b performs diggingof the digging walls while moving along allocated second digging wallareas 63 and 64. The order of digging of the second work paths 54 to 56or the order of digging of the second digging wall areas 63 and 64 maybe determined by the remote controller 2. Alternatively, the order ofdigging of the second work paths 54 to 56 or the order of digging of thesecond digging wall areas 63 and 64 may be determined by the machinecontroller of the second work machine 1 b.

For example, as illustrated in FIG. 5 , the first work machine 1 acauses the blade 18 to operate according to a target design topography84. The first work machine 1 a starts digging while traveling forwardfrom a first start point P1 on the actual topography 80 and drops thedug soil from a cliff. The first work machine 1 a travels in reverse toa second start point P2. The first work machine 1 a starts digging whiletraveling forward from the second start point P2 and drops the dug soilfrom the cliff. The first work machine 1 a travels in reverse to a thirdstart point P3. The first work machine 1 a starts digging whiletraveling forward from the third start point P3 and drops the dug soilfrom the cliff.

By repeating such work, the first work machine 1 a digs the actualtopography 80 so that the actual topography 80 has a shape along thetarget design topography 84. The second work machine 1 b also performsdigging in the same manner as the first work machine 1 a. Uponcompleting the digging of the target design topography 84, the workmachines 1 a and 1 b dig a next target design topography 85 positionedbelow the target design topography 84. The work machines 1 a and 1 brepeat the above work until they reach a final target topography 81 orits vicinity.

Next, control for preventing the work machines 1 a and 1 b in theautomatic operation mode from deviating from the work paths 51 to 56(hereinafter referred to as “deviation prevention control”) will bedescribed. FIG. 7 is a flowchart illustrating processes of the deviationprevention control executed by the remote controller 2. As illustratedin FIG. 7 , in step S201, the remote controller 2 acquires a travelingstate. The remote controller 2 acquires the traveling state from each ofthe plurality of work machines 1 a and 1 b.

The traveling state includes the current positions of the work machines1 a and 1 b, the traveling directions of the work machines 1 a and 1 b,and the rotation speeds of the left and right crawler belts of the workmachines 1 a and 1 b. The remote controller 2 acquires the currentposition of each of the work machines 1 a and 1 b from the position dataof each of the work machines 1 a and 1 b. The remote controller 2acquires the traveling direction of each of the work machines 1 a and 1b from the orientation data of each of the work machines 1 a and 1 b.The remote controller 2 acquires the current position of each of thework machines 1 a and 1 b from the position data of each of the workmachines 1 a and 1 b. The remote controller 2 acquires the rotationspeeds of the left and right crawler belts of each of the work machines1 a and 1 b from the rotation speed data of each of the work machines 1a and 1 b.

In step S202, the remote controller 2 determines an object of thedeviation prevention control. The remote controller 2 determines whethereach of the plurality of work machines 1 a and 1 b repeatedly travels ona same work path. When there are the work machine 1 a repeatedlytraveling on the same work path and the work machine 1 b repeatedlytraveling on the same work path, the remote controller 2 determines thework machines 1 a and 1 b as an object of the deviation preventioncontrol. For example, when the work machines 1 a and 1 b are travelingon the same work paths for a predetermined period of time as the workpaths on which they have traveled in the previous work, the remotecontroller 2 determines that the work machines 1 a and 1 b arerepeatedly traveling on the same work paths. That is, the remotecontroller 2 determines the work machines 1 a and 1 b that are diggingthe slots by slot dozing as the object of the deviation preventioncontrol. Therefore, for example, the remote controller 2 excludes thework machines 1 a and 1 b that are moving toward the allocated workareas from the object of the deviation prevention control.

In step S203, the remote controller 2 determines whether the workmachine that is the object of the deviation prevention control isdeviating from the work path. For example, when the first work machine 1a is traveling on the first work path 51 and is the object of thedeviation prevention control, the remote controller 2 determines whetherthe first work machine 1 a is deviating from the first work path 51.Further, when the second work machine 1 b is traveling on the secondwork path 54 and is the object of the deviation prevention control, theremote controller 2 determines whether the second work machine 1 b isdeviating from the second work path 54. The remote controller 2determines whether the first work machine 1 a is deviating from thefirst work path 51 based on the traveling state of the first workmachine 1 a. The remote controller 2 determines whether the second workmachine 1 b is deviating from the second work path 54 based on thetraveling state of the second work machine 1 b.

The remote controller 2 determines that the work machines 1 a and 1 bare deviating from the work path when at least one of first to thirdconditions is satisfied. A first condition is that a state where thetraveling directions of the work machines 1 a and 1 b are deviating fromthe target orientations of the work machines 1 a and 1 b continues for apredetermined period of time. For example, the target orientation of thefirst work machine 1 a is the first work direction D1. The targetorientation of the second work machine 1 b is the second work directionD2.

A second condition is that a deviation width of the current positions ofthe work machines 1 a and 1 b from the work paths exceed a threshold.For example, as illustrated in FIG. 8 , the deviation width is adistance W1 between a center line C1 extending in the front-backdirection of the first work machine 1 a and a center line C2 extendingin the first work direction D1 of the first work path 51. Alternatively,the deviation width may be a distance W2 between an end of the firstwork path 51 and an end of the blade 18 of the first work machine 1 a. Athird condition is that the difference in rotation speed between theleft and right crawler belts 16L and 16R is greater than a threshold.When the remote controller 2 determines that at least one of the workmachines 1 a or 1 b is deviating from the work path, the processproceeds to step S204.

In step S204, the remote controller 2 stops travel of the deviating workmachine. For example, upon determining that the first work machine 1 ais deviating from the first work path 51, the remote controller 2 stopsthe travel of the first work machine 1 a.

In step S205, the remote controller 2 stops travel of the work machinepositioned in a predetermined range. The predetermined range is the workarea adjacent to the work area of the deviating work machine. Forexample, upon determining that the first work machine 1 a is deviatingfrom the first work path 51, the remote controller 2 stops the travel ofthe first work machine 1 a. The remote controller 2 also stops travel ofthe second work machine 1 b positioned in the second work area 50Badjacent to the first work area 50A. In this case, the remote controller2 stops the travel of the second work machine 1 b even if the secondwork machine 1 b is not deviating from the second work path 54.

In step S206, the remote controller 2 switches the work machines 1 a and1 b stopped in steps S204 and S205 from the automatic operation mode tothe manual operation mode. Accordingly, the operator can manuallyoperate the stopped work machines 1 a and 1 b using the operating device5.

In the control system 100 of the work machines 1 a and 1 b according tothe present embodiment described above, it is determined whether thework machines 1 a and 1 b are deviating from the work paths 51 and 54based on the traveling state. When it is determined that the workmachines 1 a and 1 b are deviating from the work paths 51 and 54, thetravel of the work machines 1 a and 1 b is stopped. As a result, thework machines 1 a and 1 b can be prevented from deviating from the workpaths 51 and 54.

Although an embodiment has been described so far, the present inventionis not limited to the above embodiment and various modifications can bemade without departing from the gist of the invention. The work machines1 a and 1 b are not limited to bulldozers and may be other vehicles suchas wheel loaders or motor graders. The work machines 1 a and 1 b may bea vehicle driven by an electric motor.

The remote controller 2 may have a plurality of controllers that areseparate from each other. The processes by the remote controller 2 maybe distributed and executed among the plurality of controllers. Themachine controller 26 a may have a plurality of controllers that areseparate from each other. The processes by the machine controller 26 amay be distributed and executed among the plurality of controllers. Theabove-mentioned processes may be distributed and executed by a pluralityof processors.

The processes of the automatic operation and the processes of thedeviation prevention control are not limited to those of theabove-mentioned embodiment and may be changed, omitted, or added. Theexecution order of the processes of the automatic operation and theexecution order of the processes of the deviation prevention control arenot limited to those of the above-mentioned embodiment and may bechanged.

When determining that the work machines 1 a and 1 b have deviated fromthe work paths 51 and 54, the remote controller 2 may output a warning.The warning may be an image or text displayed on the display 4.Alternatively, the warning may be a sound. The deviation preventioncontrol may be applied not only when the work machines 1 a and 1 b aretraveling forward on the work paths 51 and 54, but also when they aretraveling in reverse.

A portion of the processes by the machine controller 26 a may beexecuted by the remote controller 2. A portion of the processes by theremote controller 2 may be executed by the machine controller 26 a. Forexample, the processes of the automatic operation may be executed byeach of the machine controllers of the work machines 1 a and 1 b. Theprocesses of the deviation prevention control may be executed by each ofthe machine controllers of the work machines 1 a and 1 b.

INDUSTRIAL APPLICABILITY

According to the present disclosure, it is possible to prevent the workmachine from deviating from the work path.

REFERENCE SIGNS LIST

1 a First work machine

1 b Second work machine

2 Remote controller

6 Communication device

12 Travel device

13 Work implement

16L Left crawler

16R Right crawler

26 a Machine controller

51 First work path

1. A method for controlling a first work machine including a workimplement, the method comprising: acquiring a traveling state of thefirst work machine that is performing work with the work implement whiletraveling on a first work path; determining whether the first workmachine is deviating from the first work path based on the travelingstate; and stopping travel of the first work machine upon determiningthat the first work machine is deviating from the first work path. 2.The method according to claim 1, further comprising: determining whetherthe first work machine is repeatedly traveling on the first work path;and determining whether the first work machine is deviating from thefirst work path when the first work machine is repeatedly traveling onthe first work path.
 3. The method according to claim 1, wherein thetraveling state includes a traveling direction of the first workmachine, and the method further comprising: determining that the firstwork machine is deviating from the first work path when a state in whichthe traveling direction of the first work machine is deviating from atarget orientation of the first work machine continues for apredetermined period of time.
 4. The method according to claim 1,wherein the traveling state includes a of the first work machine, andthe method further comprising: determining that the first work machineis deviating from the first work path when a deviation width of thecurrent position of the first work machine from the first work pathexceeds a threshold.
 5. The method according to claim 1, wherein thefirst work machine further includes left and right crawler belts, thetraveling state includes rotation speeds of the left and right crawlerbelts, and the method further comprising: determining that the firstwork machine is deviating from the first work path when a differencebetween the rotation speeds of the left and right crawler belts isgreater than a threshold.
 6. The method according to claim 1, furthercomprising: allocating a work path to each of a plurality of workmachines including the first work machine; acquiring traveling states ofthe plurality of work machines; determining whether any one of theplurality of work machines is deviating from the work path allocated tothe corresponding work machine based on the traveling state; andstopping travel of the work machine that is determined to be deviatingfrom the work path.
 7. The method according to claim 6, wherein theplurality of work machines further include a second work machinepositioned in a predetermined range in a vicinity of the first workmachine, and the method further comprising: stopping travel of thesecond work machine together with the first work machine upondetermining that the first work machine is deviating from the first workpath.
 8. The method according to claim 1, wherein the first work machineis controlled to dig a ground with the work implement while traveling onthe first work path so that a slot is formed.
 9. The method according toclaim 1, further comprising: determining whether the first work machinethat is traveling in reverse on the first work path is deviating fromthe first work path based on the traveling state; and stopping travel ofthe first work machine upon determining that the first work machine isdeviating from the first work path.
 10. A system for controlling a firstwork machine including a work implement, the system comprising: acommunication device configured to communicate with the first workmachine; and a remote controller configured to acquire a traveling stateof the first work machine that is performing work with the workimplement while traveling on a first work path, determine whether thefirst work machine is deviating from the first work path based on thetraveling state, and stop travel of the first work machine upondetermining that the first work machine is deviating from the first workpath.
 11. A work machine comprising: a work implement; a travel device;and a machine controller configured to control the work implement andthe travel device, the machine controller being configured to acquire atraveling state of the work machine when the work machine is performingwork while traveling on a work path, determine whether the work machineis deviating from the work path based on the traveling state, and stoptravel of the work machine upon determining that the work machine isdeviating from the work path.